The invention is concerned with a band or wire shaped material consisting of a metal alloy that contains at least phosphorus and tin, such as phosphor bronze or a similar material, and comprises an outer coating made of a tin-lead alloy.
Materials of this type are used, by preference, in the electric and electronic industries, where their solderability and corrosion resistance is of the utmost importance. It has been found, however, that materials of this type age as time goes on and lose their wettability, i.e., their solderability, as compared to liquid tin-lead alloys and tin. In the case of these known materials, it is a particular disadvantage that the aging process, that is to say the reduction of solderability, takes place within a relatively short time; periods range commonly from 5 to 12 weeks.
For the improvement of solderability, it is known already to cover a phosphor bronze wire with a layer of copper having a thickness of 2 to 8 microns, and subsequently with a layer of a tin-lead alloy having a thickness of 3 to 5 microns. Subsequently, it is possible to subject the coated wire to a fusion treatment in an electric furnace, in a neutral gas atmosphere. After this treatment, the wire is cooled in the air.